Purpose :
This an institutional, consecutive, case series describing the features observed on optical coherecne tomography angiography (OCT-A) of choroidal nevomenalocytic lesions. The purpose of this work is to:- Assess the anatomical alterations in retino-choroidal layers imaged via OCT-A assosicated with presence of choroidal nevomelanocytic lesions- Investigate the potential of OCT-A to contribute diagnostic and prognostic information.

Methods :
Consecutive patients referred with choroidal nevomelanocytic lesions to a tertiary academic ophthalmology centre underwent swept-source OCT-A by means of the DRI Triton OCT-A (Topcon Corporation, Tokyo, Japan). A scan centred on the lesion was obtained on each case. En-face structural OCT of the choriocapillaris with flow reversal was also performed. Two experienced specialists in chorio-retinal disease undertook qualitative assessment of obtained images.

Results :
45 consecutive cases of choroidal nevomelanocytic lesions underwent OCTA imaging. Of those, 25 had adequate imaging quality for further analysis. 15 represented flat choroidal nevi without suspicious features and 10 cases where choroidal nevi showing elevation on OCT. The latter cases had an average thickness of the nevus of 256 microns measured on OCT. The superficial and deep capillary plexuses appeared undisturbed in all cases. The outer retinal layer appeared normal in all cases of flat choroidal nevi. In the cases of choroidal nevi with mild elevation, the outer retinal layer appeared more susceptible to projection artifacts from overlying retinal vasculature. The choriocapillaris layer showed fading of the normal homogenous vascular mosaic corresponding to the area of the nevus. The corresponding area appeared increasingly darker with increasing thickness of the choroidal nevus. On en-face reverse flow OCT centered on the choroid, even the faintest and thinnest nevi could be visualized in striking detail allowing very precise delineation of the nevus and measurement of lateral dimensions.